
A disk in a RAID set has failed or is missing
Disk Utility monitors the status of the disks in a RAID set. If you see a message that a disk is missing or has failed, there are several things you can try to solve the problem.
- If a disk is missing, make sure it is connected to power and turned on, and that it's connected to your computer. If you are using a FireWire or USB disk, you may need to disconnect it then connect it again.
- Use the First Aid pane to repair the disks in the RAID, then check the RAID set to see if it still reports an error. You may need to unmount the RAID set to repair the disks.
- In some cases, you might need to quit and reopen Disk Utility or restart your computer and then check the RAID set.
- If you are using a mirrored RAID set, there might be an error while writing data to the disk. Click Rebuild in the RAID pane of Disk Utility.
- If you are using a striped RAID set, delete the damaged RAID set. Your data may be lost. Be sure to back up the disks in your RAID set and other data regularly.
- If you have a persistent problem with a disk in a mirrored RAID set, you may need to replace it. After you replace the damaged disk, click Rebuild to rebuild the RAID set.